This disclosure relates to a conversion system for reducing NOx emissions in locomotives and vehicles that employ hydrocarbon-based fossil fuels.
Production of emissions from mobile and stationary combustion sources such as locomotives, vehicles, power plants and the like, has resulted in environmental pollution. One particular source of such emissions is NOx emissions from vehicles. Environmental legislation restricts the amount of NOx that can be emitted by vehicles. In order to comply with this legislation, efforts have been directed at reducing the amount of NOx emissions.
One method of emission reduction is directed to minimizing the amount of NOx emissions produced during the process of combustion in engines. This method generally involves redesigning engines to optimize the combustion of fuel. This approach has resulted in the reduction of NOx over the years; however, it is expensive and all efforts so far have not resulted in any substantial reduction in NOx emissions.
Another method is directed to using an ammonia selective catalytic reactor to reduce NOx emissions. In this method, a solution of ammonia or urea contacts the exhaust stream to reduce the NOx to nitrogen, water and carbon dioxide (if urea is used). This method is disadvantageous in that toxic chemicals such as ammonia or urea have to be carried on vehicles and maintained at sufficient levels for NOx reduction.
Yet another method is the “lean NOx trap” method that involves the dispersion of metal catalysts onto substrates such as, for example, barium oxide (BaO), calcium oxide (CaO) or barium carbonate (BaCO3) to form NOx traps. When, for instance, BaO is saturated with NOx thus forming barium nitrate, Ba(NO3)2, reductants are used to reduce the Ba(NO3)2 back to BaO and nitrogen. NOx emissions into the atmosphere are then reduced in this way. The cycle is then repeated. This method requires a large NOx trap often in a dual bed arrangement. For application on a locomotive or other mobile combustion sources, this method of reducing NOx would be too expensive and would take considerable space.
It is therefore desirable to have a fuel conversion system that does not require carrying toxic chemicals, and avoids the development of expensive infrastructure for the reductant distribution. This system is efficient and inexpensive for the reduction of NOx emissions.